1. Field of the Invention
The present invention relates to vacuum seal construction and, more particularly, to techniques for fabricating a sealing flange assembly useful for oval-like and other noncircular ports in high vacuum equipment.
2. Description of the Prior Art
Vacuum vessels of various sizes and shapes are used in a wide variety of well-known commercial as well as developmental processes. In these situations, it is usually necessary that access means in the form of ports, openings and the like be provided to enable entry into the vessel interior for repairs, adjustments, workpiece removal and the like. The access ports are generally circular or oval-like in cross-section, although other shapes can of course be used. These ports must be provided with suitable vacuum sealing means, such as cover plates, doors and the like, during normal operation of the equipment.
In the past, it has been found expedient to construct the sealing surfaces of circular vacuum sealing flanges by a machining process of the turning type. A typical and well-known sealing flange amenable to fabrication by turning is shown in FIG. 13 in the Final Report UTRC-76-122 prepared under purchase order agreement with the University of Texas under United States Energy Research And Development Administration Contract E(40-1)4478. However, for oval-like and other noncircular seal shapes, this type of machining process is not available since the shape has no rotational symmetry. It is known that grinding and/or polishing offer processes by which noncircular vacuum seal flanges can alternatively be machined. These have been commonly thought to be optimum processes for fabricating vacuum sealing surfaces as a result of the very fine surface finish produced on metallic flange members, a surface finish of 8.mu. inch being representative of these processes. Although the surface finish obtainable by milling is usually inherently more coarse than that produced by grinding and/or polishing, milling also has been suggested as an alternative machining process, specifically for a sealing flange assembly which includes relatively hard metallic flange members having opposed, mating surfaces at least a portion of which are chamfered to define a V-shaped notch therebetween and a relatively soft sealing member disposed in the notch under compression against the chamfered surfaces, for example, see FIG. 13 of the above-cited Final Report UTRC-76-122.